I am respooling my curado with same braid. last time I think I put to much mono on as a backing, How much would you suggest to put on before loading up with braid?

Some people use just enough mono to prevent the braid from slipping and others a certain percentage of mono to braid (eg, 50/50 70/30, etc.).

I try to keep about 50 - 75 yards of the braid on top and the rest as mono underneath. My reasoning for this is that I want to make sure that my braid gets used up.

Given that most filler spools are about 150 yards, this enables me to fill my spool 2 to 3 times.

The ratio of braid to mono is entirely up to you. There is no right or wrong here. You just have to figure out what suits your needs.

I even use a backer for Flourcarbon too. No point in filling a reel with expensive line, when only the last 550-75 yards gets used. 50-75 yards is more than enough to allow several cut/re-ties before needing more line.

I agree with using 50-75 yards of the line you actually fish with. After all, you'll probably want to respool once you've lost 20 yards or so, so why throw away more line than necessary?